The invention relates generally to medical connectors of the type used in the handling and administration of parenteral fluids, and more particularly, to a needle free connector employing a valve mechanism that compensates for negative fluid displacement, i.e., drawing fluid into the connector, as the connector returns to its unaccessed state from an accessed state.
Within this specification the terms, “negative-bolus effect,” “positive-bolus effect,” and “no-bolus effect” are used to describe the operating characteristics of medical connectors as the connector returns to its unaccessed state from an accessed state. “Negative-bolus” effect describes the condition during which fluid is drawn into the connector as the connector returns to its unaccessed state from an accessed state. “Positive-bolus effect” describes the condition during which fluid is expelled out of the connector as the connector returns to its unaccessed state from an accessed state. “No-bolus effect” describes the condition during which fluid displacement is neutralized and fluid is neither drawn into nor expelled out of the connector as the connector returns to its unaccessed state from an accessed state.
Needle free medical connectors for injecting fluid into or removing fluid from an intravenous (“IV”) fluid administration set are well known and widely used. One conventional type of such a connector includes a housing having connection ports at both ends. One connection port may comprise a female Luer port sized to receive a blunt male cannula, such as a male Luer taper. The other connection port may be located opposite the first port but in some cases is located at a ninety degree or other angle to the first port, and comprises a male Luer fitting. In many cases the second port of the connector is permanently connected to IV tubing which in turn is connected to an IV catheter that communicates with a patient's venous system.
A valve is located within the connector and in most cases uses the housing of the connector as part of the valve mechanism. When the connector is accessed, the valve opens an internal fluid passageway between the first and second ports. In some connectors, the internal fluid passageway is defined by the internal boundaries of the connector housing; in other connectors it is defined by an internal cannula or hollow spike; and still in others, the internal fluid passageway is defined by a compressible tubular body that carries the valve mechanism.
Many needle free medical connectors create fluid displacement as the connector is accessed and unaccessed. As the connector is accessed by a blunt male Luer cannula tip inserted into the inlet or first port of the connector housing, the valve mechanism is engaged. In some connectors, the blunt cannula tip penetrates a valve device to establish fluid communication with the internal fluid flow path of the connector. In other connectors, the blunt cannula tip displaces a valve device without penetrating it in order to establish fluid communication with the fluid flow path. In either case, the volumetric capacity of the fluid flow path is often reduced by the insertion of the blunt cannula when accessing the connector. Subsequently, when the blunt cannula is removed from the connector, the volumetric capacity of the fluid flow path increases. This increase in the volumetric capacity may create a partial vacuum or pressure reduction in the fluid flow path that may draw fluid into the connector from the second or downstream end of the connector. As previously mentioned, the effect of drawing fluid into the connector in this manner is referred to as a “negative-bolus” effect in that a quantity, or “bolus,” of fluid is drawn into the partial vacuum or reduced pressure location within the connector.
A negative-bolus effect as the connector returns to its unaccessed state is undesirable to some medical care providers and either a neutral bolus or positive bolus effect is preferred. It is therefore desirable to arrange for a valve mechanism that either does not affect the capacity of the internal fluid passageway through the connector as the connector is returned to its unaccessed state, or that actually decreases it.
In one approach, the negative-bolus effect may be reduced or eliminated by clamping the IV tubing between the connector and the IV catheter prior to removal of the blunt cannula from the connector. This prevents the back flow of fluid through the IV catheter and into the connector. However this is an undesirable approach in that another device, i.e. a clamp, is necessary and the care provider must remember to engage the clamp with the tubing. Furthermore, the use of additional devices adds expense and causes inconvenience in that they may not be available at the time needed. Additional steps are also undesirable in that most care providers are very busy already and would therefore naturally prefer to reduce the number of steps in providing effective care to patients rather than increase the number.
In another approach, one that disadvantageously also increases the number of steps in the administration of medical fluids, the operator continually injects fluid into the connector from the male device while the male device is being disengaged from the connector. By continuously adding fluid the operator attempts to fill the increasing fluid volume of the fluid flow path through the connector as the male Luer is being withdrawn, thereby reducing the likelihood of a partial vacuum and thus the likelihood of a negative bolus forming in the fluid flow path. However, this approach is also undesirable in that not only does it add a step but may require some skill in successfully carrying out the procedure.
The negative-bolus effect may also be reduced by the design of the medical connector. As previously mentioned, some medical connectors include an internal cannula or hollow spike housed inside the connector body. The internal cannula or spike is positioned to force open a septum upon depression of the septum onto the internal cannula or spike by a blunt cannula. The internal cannula or spike has an orifice at the top and, upon depression of the septum over the internal cannula or spike, the internal cannula or spike is put directly into fluid communication with the blunt cannula. The internal cannula or spike provides a generally fixed-volume fluid-flow path through the connector. Thus, as the septum returns to its closed position the partial vacuum formed within the connector, if any, is not as large as the partial vacuum formed in a connector having a more volumetrically variable internal fluid passageway. A disadvantage of typical connectors having an internal cannula or spike is a lower fluid-flow rate caused by the small lumen in the cannula or spike. Additionally, it has been noted that with the connector design having a fixedly-mounted internal spike and a movable septum that is pierced by that spike to permit fluid flow, such pierced septum may be damaged with multiple uses and a leaking connector may result.
Another connector provides a valve mechanism that includes a flexible body within which is located a relatively rigid leaf spring. The housing of the connector includes an internal cannula and upon depression of the flexible body by the introduction of a blunt cannula through a port, the internal cannula forces the leaves of the leaf spring apart. The leaves in turn force the top of the flexible body apart and open a slit contained therein. The opening of the slit establishes fluid communication between the accessing blunt cannula and the lumen of the internal cannula. The expanding leaf spring also creates a reservoir-type area between the flexible body and the outer wall of the internal cannula in which fluid is held. As the external blunt cannula is removed from the connector, the leaf spring and reservoir collapse and fluid is forced out of the reservoir and into the internal cannula lumen.
This positive displacement of fluid may result in a positive bolus effect as the valve returns to its unaccessed state. However, the valve mechanism is relatively complex with a leaf spring being incorporated into a flexible member which adds some manufacturing concerns as well as at least one additional part; i.e., the leaf spring. Manufacturing concerns and additional parts can tend to cause expenses to rise, an undesirable effect in the health care industry today where manufacturers strive to provide effective products at lower costs. Further, the reservoir-type system does not permit continuous flow through the entire expandable flexible body section. Instead, fluid flows into the reservoir and is retained there until the valve is returned to its unaccessed state.
Hence, those concerned with the development of medical connectors have recognized the need for a medical connector having a valve mechanism that avoids the negative-bolus effect by producing either a positive-bolus effect or a no-bolus effect. The need for a medical connector that provides these effects without sacrificing fluid-flow rate or structural simplicity has also been recognized. Further needs have also been recognized such as the need for a medical connector that is less expensive to manufacture, that is efficient in operation, and that includes fewer parts. The present invention addresses such needs and others.